diff --git a/ext2spice/ext2spice.c b/ext2spice/ext2spice.c
index f909b203..d2a43c38 100644
--- a/ext2spice/ext2spice.c
+++ b/ext2spice/ext2spice.c
@@ -3552,14 +3552,14 @@ spcnAPHier(
 
 int
 spcdevOutNode(
-    HierName *prefix,
-    HierName *suffix,
-    char *name,
+    const HierName *prefix,
+    const HierName *suffix,
+    const char *name,
     FILE *outf)
 {
     HashEntry *he;
     EFNodeName *nn;
-    char *nname;
+    const char *nname;
 
     he = EFHNConcatLook(prefix, suffix, name);
     if (he == NULL)
diff --git a/ext2spice/ext2spice.h b/ext2spice/ext2spice.h
index bd83ef67..0f39253b 100644
--- a/ext2spice/ext2spice.h
+++ b/ext2spice/ext2spice.h
@@ -48,7 +48,7 @@ extern void setDevMult(int i, float f);
 /* C99 compat */
 extern int EFHNSprintf(char *str, HierName *hierName);
 extern int printSubcktDict(void);
-extern int spcdevOutNode(HierName *prefix, HierName *suffix, char *name, FILE *outf);
+extern int spcdevOutNode(const HierName *prefix, const HierName *suffix, const char *name, FILE *outf);
 extern int spcnAP(DevTerm *dterm, EFNode *node, int resClass, float scale, char *asterm, char *psterm, float m, FILE *outf, int w);
 extern int parallelDevs(const devMerge *f1, const devMerge *f2);
 extern int nodeHspiceName(char *s);